Softbit Standards Specification for AC Electric Motors
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Before we start describing the details of Indian standards, we first give details of some of the Australian Engineering standards and tests.

Electric Motor Standards and Tests:
When purchasing an electric motor, the specification will list a number of Engineering Standards that the motor will have to meet. These will determine the details of the motor type, size, speed, winding insulation, cooling system and required temperature rise limits, mounting and the tests that the motor must be subjected to during manufacture. Other items will detail the starting characteristics, the vibration and noise levels, the inbuilt thermal protection devices required, use of anti-condensation heaters, requirement for special lubrication systems and bearings, use of porous plugs and type of painting. The protection required during transport and lifting facilities can also be specified.

Generally the larger electric motors would be expected to comply with at least the following Australian Engineering Standards or their equivalent:
· AS 1359 parts 4; 50; 60; 69 - Rotating Electrical Machines;
· AS 1081 & AS 1469 - Noise Levels;
· IEC 34-6: 1991 - Methods of Cooling; and
· AS 1939 - Protection Degree Ratings of Enclosures

The performance tests required during manufacture are specified to be in accordance with AS 1359 part 60 or its equivalent. It is normal to require that the first motor of a design be subjected to a more stringent set of tests than subsequent motors of the same design. This series of tests are called 'Type Tests'. The tests normally required for type tests are as follows:
· Resistance of windings;
· No-load losses and current;
· Locked rotor test (see description below);
· Temperature rise (see description below);
· Power factor;
· Efficiency;
· Momentary overload;
· Medium voltage insulation (as per AS 1359 Pt. 60);
· Vibration (as per the requirements of AS 1359 Pt. 50 or equivalent);
· Noise (as per AS 1081 with the level as described in AS 1469); and
· Determination of run-up speed/torque characteristic

If the proposed manufacturer has previously produced this type of motor and has carried out the required type tests, less stringent test may be allowed. These less stringent tests are known as 'duplicate' tests and include the following:

· Resistance of windings;
· No-load losses and current;
· Locked rotor (see description below);
· Medium voltage insulation;
· Vibration

Test Certificates are required for all tests and should show the results and description of all tests.
Locked Rotor Tests are performed with the rotor locked to establish starting torques and starting currents. Starting torque can be evaluated using a torque arm, which locks the rotor. The voltage is slowly increased until full load current circulates in the stator winding. It is preferable to carry out this test at 100% rated voltage but if this is not possible (due to the potential of damaging the motor and/or the limitations of the test facilities), the voltage can be raised in equal increments up to 50% rated voltage. A curve is then drawn through the plotted values and extrapolated to the 100% rated voltage value.

Temperature Tests are conducted in two parts:
A no-load test which provides full voltage iron loss for the motor - the motor is uncoupled and run at full voltage until thermal equilibrium is reached; and
A full load test at full copper loss - the motor is coupled to a load, as close to full load as the test facility will allow, the voltage reduced until full load current is reached and the motor run until thermal equilibrium is reached.

A record of all readings, including temperature, voltage and current, are to be supplied as part of the test results. Note that, if anti-condensation heaters are fitted, then these are to be energized while the test is in progress. To satisfy the specified requirements, the motor temperature rise should not exceed that specified.
The Insulation Class on the windings, the maximum Temperature Rise under full load conditions and the maximum ambient temperature are usually specified together. For example, the specification could require a motor whose windings are to have insulation of 'F' Class and a maximum temperature rise of 800° C when operating at an ambient temperature of 400° C.
Terminals are usually described to suit the cabling requirement of size and direction of location of the cables on the side or top of the motor.

INDIAN STANDARD SPECIFICATIONS

1. PREFERRED VOLTAGES AND OUTPUTS
As per IS: 325 1978 preferred voltages and out puts are given in Fig.57 at three phase 50 HZ

2. CLASSES OF DUTY
The classes of duty are given in Fig58. For the duty type S2 the abbreviation is followed by an indication of the duration of duty.

3. LIMITS OF TEMPERATURES AND TEMPERATURE RISES
Fig.59 Gives the limits of permissible temperature rise above the cooling medium for motors insulated with materials of class ‘A’,’E’, ’B’,’F’,’H’

4. RATING PLATE
A rating plate stating the details as shown in Fig should be provided with each motor.

5. SCHEDULE OF TOLERANCES
Fig 60 gives the schedule of tolerances regarding efficiency, total losses, power factor, breakaway torque, pullout torque, moment of inertia etc.

6. ROUTINE AND TYPE TESTS
Fig.61 Gives the list of routine and type tests to be carried out normally at the manufacturer’s works.

7. METHODS OF MEASUREMENT OF TEMPERATURE RISE
Fig 62 give the methods of measurement of temperature rise.

8.CORRECTION OF TEMPERATURE RISE WITH ALTITUDE
Fig gives the table for the correction of temperature rise figures with altitudes.

9. AMBEINT TEMPERATURES AT DIFFERENT ALTITUDES AND DIFFERENT CLASS OF INSULATION WITH CORRECTION OF TEMPERATURE RISE
Fig.63 Gives the table for the assumed ambient temperatures at different altitudes, and the correction of temperature rise.

10. HIGH VOLTAGE TEST
The procedure for carrying out high voltage test is given in Fig. 64 along with test voltage.
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